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. 2016 Apr;8(4):642-63.
doi: 10.18632/aging.100895.

The Effects of Graded Levels of Calorie Restriction: VI. Impact of Short-Term Graded Calorie Restriction on Transcriptomic Responses of the Hypothalamic Hunger and Circadian Signaling Pathways

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Free PMC article

The Effects of Graded Levels of Calorie Restriction: VI. Impact of Short-Term Graded Calorie Restriction on Transcriptomic Responses of the Hypothalamic Hunger and Circadian Signaling Pathways

Davina Derous et al. Aging (Albany NY). .
Free PMC article

Abstract

Food intake and circadian rhythms are regulated by hypothalamic neuropeptides and circulating hormones, which could mediate the anti-ageing effect of calorie restriction (CR). We tested whether these two signaling pathways mediate CR by quantifying hypothalamic transcripts of male C57BL/6 mice exposed to graded levels of CR (10 % to 40 %) for 3 months. We found that the graded CR manipulation resulted in upregulation of core circadian rhythm genes, which correlated negatively with circulating levels of leptin, insulin-like growth factor 1 (IGF-1), insulin, and tumor necrosis factor alpha (TNF-α). In addition, key components in the hunger signaling pathway were expressed in a manner reflecting elevated hunger at greater levels of restriction, and which also correlated negatively with circulating levels of insulin, TNF-α, leptin and IGF-1. Lastly, phenotypes, such as food anticipatory activity and body temperature, were associated with expression levels of both hunger genes and core clock genes. Our results suggest modulation of the hunger and circadian signaling pathways in response to altered levels of circulating hormones, that are themselves downstream of morphological changes resulting from CR treatment, may be important elements in the response to CR, driving some of the key phenotypic outcomes.

Keywords: calorie restriction; circadian rhythm; hunger; hypothalamus; transcriptomics.

Conflict of interest statement

Conflict of interest statement

The authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Log Fold change of differentially expressed genes in at least one treatment relative to 12 hour ad libitum feeding (12AL). Blue indicates down-regulation and red upregulation relative to 12AL. 10CR, 20CR, 30CR and 40CR refer to 10 %, 20 %, 30 % and 40 % restriction and 24AL to 24h ad libitum feeding.
Figure 2
Figure 2
Significantly differentially regulated biological processes after three months of CR treatment, based on genes altered across CR, visualized as an Enrichment map (Cytoscape). The nodes represent biological processes, and edges represent overlap between genes in these processes. The color of the nodes represents the significance according to the p-value (white: p-value = 0.05, purple: p-value < 0.01). The size of the nodes corresponds to the size of the gene set. The width of edges is based on similarity coefficients (> 0.5) between the nodes, derived from the overlap of the gene sets underlying the processes.
Figure 3
Figure 3
Effect of graded calorie restriction on circulating hormone levels and genes involved in hunger signaling. (A) Genes involved in hunger signaling based on log fold change relative to ad libitum feeding for 12h per day (12AL) and their correlation coefficient with circulating hormone levels. Blue indicates down-regulation and red upregulation relative to 12AL. Purple indicates a negative correlation coefficient and green a positive correlation with circulating hormone levels. 10CR, 20CR, 30CR and 40CR refers to 10 %, 20 %, 30 % and 40 % restriction and 24AL to 24h ad libitum feeding. (B) Expression levels of key hunger genes plotted against circulating hormone levels. Those genes with a significant correlation based on p-value < 0.05 are included in the plot. (C) Overview of key hunger signaling genes correlating with circulating hormone levels. The lines connecting genes and hormones represent correlations and the width of these lines indicates the strength of the correlation coefficient. Green indicates a positive correlation and purple a negative correlation.
Figure 4
Figure 4
The hunger signaling pathway constructed in the IPA program colored according to genes correlating with circulating leptin levels. Red indicates a positive correlation coefficient and green indicates a negative correlation coefficient. Intensity of the color is related to the strength of the correlation.
Figure 5
Figure 5
Effect of graded calorie restriction on circulating hormone levels and genes involved in circadian rhythm. (A) Genes involved in circadian rhythm pathways based on their log fold change relative to ad libitum feeding for 12h per day (12AL) and their correlation coefficient with circulating hormone levels. Blue indicates down-regulation and red upregulation relative to 12AL. Purple indicates a negative correlation coefficient and green a positive correlation with circulating hormone levels. 10CR, 20CR, 30CR and 40CR refers to 10 %, 20 %, 30 % and 40 % restriction and 24AL refers to 24h ad libitum feeding. (B) Expression levels of core clock genes plotted against circulating hormone levels. Those genes with a significant correlation based on p-value < 0.05 are included in the plot. (C) Overview of core clock genes correlating with circulating hormone levels. The lines connecting hormones and genes represent correlations and the width of these lines indicate the strength of the correlation coefficient. Green indicates a positive correlation and purple a negative correlation.
Figure 6
Figure 6
Genes involved in circadian rhythm pathway constructed in the IPA program colored according their correlation with circulating levels of tumor necrosis factor alpha (TNF-α). Red indicates a positive correlation coefficient while green indicates a negative correlation coefficient. Intensity of the color is related to the strength of the correlation.
Figure 7
Figure 7
Prediction effect plots of the linear model with eigenvector values of principle component 1 (representing phenotypic responses) and gene expression levels of key hunger genes. A cut-off value of p-value < 0.05 was used to determine significant relationships in these linear models. Non-significance is indicated by light grey.
Figure 8
Figure 8
Prediction effect plots of the linear model with eigenvector values of principle component 1 (representing phenotypic responses) and gene expression levels of core clock genes. A cut-off value of p-value < 0.05 was used to determine significant relationships in these linear models. Non-significance is indicated by light grey.

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